Deployable solar arrays are typically contained in a small envelope when their space vehicle is launched. They are later deployed to an extended configuration to expose areas of solar collectors. Examples of such arrays are shown in the following United States patents:
Avilov--U.S. Pat. No. 3,460,992
Harvey et al--U.S Pat. No. 5,296,044
Everman et al--U.S. Pat. No. 5,487,791
A review of these patents will disclose remarkable efforts to reduce the weight and increase the reliability of these arrays. Cost, while important, has been and still is subordinate zoo reliability. The failure of an array to deploy and to survive for its full design life can result in loss of value of the entire craft and its payload. The cost of the craft and its payload is many times that of the array, especially when the payload is unique and employed for very advanced applications.
Because of this, and because of the relatively small number of vehicles involved, the design and manufacture of solar panels and their supporting structure has tended toward the complex, familiar, and costly. They have been carefully and slowly built, almost in a "handicraft" sense.
However, with the advent of space-based communication systems, the market for satellites has greatly enlarged. The cost of the payloads, while still considerable, has decreased. Expenses which are tolerable for a few very high value vehicles become unacceptable when the production count will run into the hundreds.
The demand for such a large number of arrays threatens to outstrip the capacity of existing manufacturing plants that were sufficient for the previous slow-paced demand. Multiplying plant capacity can permit faster production schedules, provided that additional skilled personnel can be found, and provided that the additional capital is available. Still the arrays would remain at least as costly.
Also, the problems of producibility remain. Existing constructions are built very painstakingly, because if one part is imperfectly produced, a large part of the entire array often must be scrapped or reworked at considerable cost. This risk and the unfavorable consequences which inevitably occur, has reduced the yield of these arrays.
It is an object of this invention to provide a solar panel which can be efficiently manufactured to high standards, and should some part of it be unsuitable, can be quickly and easily repaired or replaced. Thus the entire assembly need no longer be hostage to the acceptability of every part. Instead, all parts will be individually and readily replaceable.
With this invention, it appears likely that an array which formerly required a few months to build, can be built in a day.
However, manufacturing problems are not the only ones solved by this invention. In order to build a truly lightweight structure, the materials of construction must themselves be lightweight, and will often lack much structural strength while in a gravitational field, or in the fields of force that exist at launch or in transporting it to the site where it will be installed. To overcome this, conventional arrays simply provided more strength with more structure, and more cost.
These arrays must be stored in such a way that they can be placed in a container which can be handled on the ground without extreme care, and which will protect the array from the large launching forces. Then, when the craft is in orbit, the container must permit the delicate solar blanket controllably to be deployed from the craft and be fully protected during its removal from the container and extension to the deployed configuration. It is an object of this invention to provide such a container.
This still does not exhaust the problems of most existing arrays. Their tendency is to deploy the structure and lock it physically into a rigid structure. While there are no net gravitational forces on it while in orbit, a solar array is subject to substantial internal forces, especially to those which occur during the time while the craft leaves the shadow of the earth and comes into the sunlight. All too often, the different local expansions of material, and stacked-up dimensional tolerances, result in a hard physical snap as relative dimensions of the various parts change. While a solid lock that rigidifies the structure will assure that the structure will remain intact and deployed when it snaps, such forces can be damaging to the delicate parts of an array.
In the course of simplifying the array of this invention, the applicants have taken a different approach to cause and to assure deployment, which eliminates risk of the snapping action which is experienced in much of the prior art.
The consequence of these improvements is to increase the productivity and yield of solar arrays while still providing excellent reliability, at a significantly lower cost.